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zshexpn(1)                                                          zshexpn(1)




NAME

       zshexpn - zsh expansion and substitution


DESCRIPTION

       The  following types of expansions are performed in the indicated order
       in five steps:

       History Expansion
              This is performed only in interactive shells.

       Alias Expansion
              Aliases are expanded immediately  before  the  command  line  is
              parsed as explained under Aliasing in zshmisc(1).

       Process Substitution
       Parameter Expansion
       Command Substitution
       Arithmetic Expansion
       Brace Expansion
              These  five  are performed in one step in left-to-right fashion.
              After these expansions, all unquoted occurrences of the  charac-
              ters `\', `'' and `"' are removed.

       Filename Expansion
              If  the  SH_FILE_EXPANSION option is set, the order of expansion
              is modified for compatibility with sh and  ksh.   In  that  case
              filename  expansion  is performed immediately after alias expan-
              sion, preceding the set of five expansions mentioned above.

       Filename Generation
              This expansion, commonly referred to as globbing, is always done
              last.

       The following sections explain the types of expansion in detail.



HISTORY EXPANSION

       History  expansion  allows you to use words from previous command lines
       in the command line you are typing.  This simplifies  spelling  correc-
       tions and the repetition of complicated commands or arguments.  Immedi-
       ately before execution, each command is saved in the history list,  the
       size  of  which  is controlled by the HISTSIZE parameter.  The one most
       recent command is always retained in any case.  Each saved  command  in
       the  history  list  is called a history event and is assigned a number,
       beginning with 1 (one) when the shell starts up.   The  history  number
       that  you  may see in your prompt (see EXPANSION OF PROMPT SEQUENCES in
       zshmisc(1)) is the number that is to be assigned to the next command.


   Overview
       A history expansion begins with the first character  of  the  histchars
       parameter,  which is `!' by default, and may occur anywhere on the com-
       mand line; history expansions do not nest.  The `!' can be escaped with
       `\' or can be enclosed between a pair of single quotes ('') to suppress
       its special meaning.  Double quotes will not work for this.   Following
       this history character is an optional event designator (see the section
       `Event Designators') and then an optional word designator (the  section
       `Word  Designators');  if  neither  of these designators is present, no
       history expansion occurs.

       Input lines  containing  history  expansions  are  echoed  after  being
       expanded,  but  before  any  other expansions take place and before the
       command is executed.  It is this expanded form that is recorded as  the
       history event for later references.

       By  default, a history reference with no event designator refers to the
       same event as any preceding history reference on that command line;  if
       it  is the only history reference in a command, it refers to the previ-
       ous command.  However, if the option CSH_JUNKIE_HISTORY  is  set,  then
       every  history  reference  with no event specification always refers to
       the previous command.

       For example, `!' is the event designator for the previous  command,  so
       `!!:1'  always  refers  to  the first word of the previous command, and
       `!!$' always refers to the last word of  the  previous  command.   With
       CSH_JUNKIE_HISTORY set, then `!:1' and `!$' function in the same manner
       as `!!:1' and `!!$', respectively.  Conversely,  if  CSH_JUNKIE_HISTORY
       is  unset,  then  `!:1'  and  `!$'  refer  to the first and last words,
       respectively, of the same event referenced by the nearest other history
       reference  preceding them on the current command line, or to the previ-
       ous command if there is no preceding reference.

       The character sequence `^foo^bar' (where `^'  is  actually  the  second
       character of the histchars parameter) repeats the last command, replac-
       ing the string foo with bar.  More precisely, the sequence  `^foo^bar^'
       is synonymous with `!!:s^foo^bar^', hence other modifiers (see the sec-
       tion  `Modifiers')  may  follow  the   final   `^'.    In   particular,
       `^foo^bar^:G' performs a global substitution.

       If  the  shell encounters the character sequence `!"' in the input, the
       history mechanism is temporarily disabled until the current  list  (see
       zshmisc(1))  is  fully parsed.  The `!"' is removed from the input, and
       any subsequent `!' characters have no special significance.

       A less convenient but more comprehensible form of command history  sup-
       port is provided by the fc builtin.

   Event Designators
       An  event designator is a reference to a command-line entry in the his-
       tory list.  In the list below, remember that the initial  `!'  in  each
       item  may  be  changed  to  another  character by setting the histchars
       parameter.

       !      Start a history expansion, except when followed by a blank, new-
              line,  `=' or `('.  If followed immediately by a word designator
              (see the section `Word Designators'), this forms a history  ref-
              erence with no event designator (see the section `Overview').

       !!     Refer  to  the  previous  command.   By  itself,  this expansion
              repeats the previous command.

       !n     Refer to command-line n.

       !-n    Refer to the current command-line minus n.

       !str   Refer to the most recent command starting with str.

       !?str[?]
              Refer to the most recent command containing str.   The  trailing
              `?'  is necessary if this reference is to be followed by a modi-
              fier or followed by any text that is not to be  considered  part
              of str.

       !#     Refer  to the current command line typed in so far.  The line is
              treated as if it were complete up  to  and  including  the  word
              before the one with the `!#' reference.

       !{...} Insulate a history reference from adjacent characters (if neces-
              sary).

   Word Designators
       A word designator indicates which word or words of a given command line
       are to be included in a history reference.  A `:' usually separates the
       event specification from the word designator.  It may be  omitted  only
       if  the  word designator begins with a `^', `$', `*', `-' or `%'.  Word
       designators include:

       0      The first input word (command).
       n      The nth argument.
       ^      The first argument.  That is, 1.
       $      The last argument.
       %      The word matched by (the most recent) ?str search.
       x-y    A range of words; x defaults to 0.
       *      All the arguments, or a null value if there are none.
       x*     Abbreviates `x-$'.
       x-     Like `x*' but omitting word $.

       Note that a `%' word designator works only when used in  one  of  `!%',
       `!:%'  or `!?str?:%', and only when used after a !? expansion (possibly
       in an earlier command).  Anything else results in  an  error,  although
       the error may not be the most obvious one.

   Modifiers
       After  the  optional  word designator, you can add a sequence of one or
       more of the following modifiers, each preceded by a `:'.   These  modi-
       fiers  also  work  on  the  result of filename generation and parameter
       expansion, except where noted.

       a      Turn a file name into an absolute path:   prepends  the  current
              directory, if necessary, and resolves any use of `..' and `.' in
              the path.  Note that the transformation takes place even if  the
              file or any intervening directories do not exist.

       A      As  `a',  but also resolve use of symbolic links where possible.
              Note that resolution of `..' occurs before  resolution  of  sym-
              bolic  links.   This  call is equivalent to a unless your system
              has the realpath system call (modern systems do).

       c      Resolve a command name into an absolute path  by  searching  the
              command path given by the PATH variable.  This does not work for
              commands containing directory parts.  Note also that  this  does
              not  usually  work as a glob qualifier unless a file of the same
              name is found in the current directory.

       e      Remove all but the part of the filename extension following  the
              `.';  see  the  definition  of  the  filename  extension  in the
              description of the r modifier below.   Note  that  according  to
              that definition the result will be empty if the string ends with
              a `.'.

       h      Remove a trailing pathname component, leaving  the  head.   This
              works like `dirname'.

       l      Convert the words to all lowercase.

       p      Print  the  new  command but do not execute it.  Only works with
              history expansion.

       q      Quote the substituted  words,  escaping  further  substitutions.
              Works with history expansion and parameter expansion, though for
              parameters it is only useful if the  resulting  text  is  to  be
              re-evaluated such as by eval.

       Q      Remove one level of quotes from the substituted words.

       r      Remove a filename extension leaving the root name.  Strings with
              no filename extension are not altered.  A filename extension  is
              a `.' followed by any number of characters (including zero) that
              are neither `.' nor `/' and that continue  to  the  end  of  the
              string.  For example, the extension of `foo.orig.c' is `.c', and
              `dir.c/foo' has no extension.

       s/l/r[/]
              Substitute r for l as described below.  The substitution is done
              only  for  the  first string that matches l.  For arrays and for
              filename generation, this applies to each word of  the  expanded
              text.  See below for further notes on substitutions.

              The  forms  `gs/l/r' and `s/l/r/:G' perform global substitution,
              i.e. substitute every occurrence of r for l.  Note that the g or
              :G must appear in exactly the position shown.

              See further notes on this form of substitution below.

       &      Repeat  the  previous  s  substitution.  Like s, may be preceded
              immediately by a g.  In parameter expansion the  &  must  appear
              inside braces, and in filename generation it must be quoted with
              a backslash.

       t      Remove all leading pathname components, leaving the tail.   This
              works like `basename'.

       u      Convert the words to all uppercase.

       x      Like  q, but break into words at whitespace.  Does not work with
              parameter expansion.

       The s/l/r/ substitution works as follows.   By  default  the  left-hand
       side  of  substitutions  are  not patterns, but character strings.  Any
       character can be used as the delimiter in place of  `/'.   A  backslash
       quotes   the   delimiter   character.    The   character  `&',  in  the
       right-hand-side r, is replaced by the text from the  left-hand-side  l.
       The  `&'  can  be  quoted with a backslash.  A null l uses the previous
       string either from the previous l or from the contextual scan string  s
       from  `!?s'.  You can omit the rightmost delimiter if a newline immedi-
       ately follows r; the rightmost `?' in a context scan can  similarly  be
       omitted.  Note the same record of the last l and r is maintained across
       all forms of expansion.

       Note that if a `&' is used within glob qualifers an extra backslash  is
       needed as a & is a special character in this case.

       If  the  option HIST_SUBST_PATTERN is set, l is treated as a pattern of
       the usual form described in  the  section  FILENAME  GENERATION  below.
       This can be used in all the places where modifiers are available; note,
       however, that in globbing qualifiers parameter substitution has already
       taken  place,  so parameters in the replacement string should be quoted
       to ensure they are replaced at the correct time.  Note also  that  com-
       plicated  patterns  used  in  globbing qualifiers may need the extended
       glob qualifier notation (#q:s/.../.../) in order for the shell to  rec-
       ognize the expression as a glob qualifier.  Further, note that bad pat-
       terns in the substitution are not subject to the NO_BAD_PATTERN  option
       so will cause an error.

       When  HIST_SUBST_PATTERN  is set, l may start with a # to indicate that
       the pattern must match at the start of the string  to  be  substituted,
       and a % may appear at the start or after an # to indicate that the pat-
       tern must match at the end of the string to be substituted.  The % or #
       may be quoted with two backslashes.

       For  example,  the following piece of filename generation code with the
       EXTENDED_GLOB option:

              print *.c(#q:s/#%(#b)s(*).c/'S${match[1]}.C'/)

       takes the expansion of *.c and  applies  the  glob  qualifiers  in  the
       (#q...)  expression, which consists of a substitution modifier anchored
       to the start and end of each word (#%).  This turns  on  backreferences
       ((#b)),  so  that  the  parenthesised subexpression is available in the
       replacement string as ${match[1]}.  The replacement string is quoted so
       that the parameter is not substituted before the start of filename gen-
       eration.

       The following f, F, w and W modifiers work only with  parameter  expan-
       sion and filename generation.  They are listed here to provide a single
       point of reference for all modifiers.

       f      Repeats the immediately (without  a  colon)  following  modifier
              until the resulting word doesn't change any more.

       F:expr:
              Like  f,  but repeats only n times if the expression expr evalu-
              ates to n.  Any character can be used instead  of  the  `:';  if
              `(',  `[',  or `{' is used as the opening delimiter, the closing
              delimiter should be ')', `]', or `}', respectively.

       w      Makes the immediately following modifier work on  each  word  in
              the string.

       W:sep: Like  w  but  words are considered to be the parts of the string
              that are separated by sep. Any character can be used instead  of
              the `:'; opening parentheses are handled specially, see above.


PROCESS SUBSTITUTION

       Each  part  of  a  command  argument  that  takes  the  form `<(list)',
       `>(list)' or `=(list)' is subject to process substitution.  The expres-
       sion  may be preceded or followed by other strings except that, to pre-
       vent clashes with commonly occurring strings  and  patterns,  the  last
       form  must  occur at the start of a command argument, and the forms are
       only expanded when  first  parsing  command  or  assignment  arguments.
       Process  substitutions  may be used following redirection operators; in
       this case, the substitution must appear with no trailing string.

       In the case of the < or > forms, the shell runs the commands in list as
       a  subprocess of the job executing the shell command line.  If the sys-
       tem supports the /dev/fd mechanism, the command argument is the name of
       the  device  file corresponding to a file descriptor; otherwise, if the
       system supports named pipes (FIFOs), the command  argument  will  be  a
       named  pipe.   If the form with > is selected then writing on this spe-
       cial file will provide input for list.  If < is  used,  then  the  file
       passed  as  an  argument  will  be  connected to the output of the list
       process.  For example,

              paste <(cut -f1 file1) <(cut -f3 file2) |
              tee >(process1) >(process2) >/dev/null

       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
       the  results  together,  and  sends  it  to  the processes process1 and
       process2.

       If =(...) is used instead of <(...), then the file passed as  an  argu-
       ment  will be the name of a temporary file containing the output of the
       list process.  This may be used instead of the <  form  for  a  program
       that expects to lseek (see lseek(2)) on the input file.

       There is an optimisation for substitutions of the form =(<<<arg), where
       arg is a single-word argument to the here-string redirection <<<.  This
       form produces a file name containing the value of arg after any substi-
       tutions have been performed.  This is handled entirely within the  cur-
       rent  shell.   This  is  effectively  the  reverse  of the special form
       $(<arg) which treats arg as a file name and replaces it with the file's
       contents.

       The = form is useful as both the /dev/fd and the named pipe implementa-
       tion of <(...) have drawbacks.  In the former case, some programmes may
       automatically  close  the  file descriptor in question before examining
       the file on the command line, particularly if  this  is  necessary  for
       security  reasons such as when the programme is running setuid.  In the
       second case, if the programme does not actually open the file, the sub-
       shell  attempting  to read from or write to the pipe will (in a typical
       implementation, different operating systems may have  different  behav-
       iour)  block for ever and have to be killed explicitly.  In both cases,
       the shell actually supplies the information using a pipe, so that  pro-
       grammes  that expect to lseek (see lseek(2)) on the file will not work.

       Also note that the previous example can be  more  compactly  and  effi-
       ciently written (provided the MULTIOS option is set) as:

              paste <(cut -f1 file1) <(cut -f3 file2) \
              > >(process1) > >(process2)

       The  shell  uses  pipes  instead  of  FIFOs to implement the latter two
       process substitutions in the above example.

       There is an additional problem with >(process); when this  is  attached
       to  an  external command, the parent shell does not wait for process to
       finish and hence an immediately following command cannot  rely  on  the
       results  being  complete.   The  problem  and  solution are the same as
       described in the section MULTIOS in zshmisc(1).  Hence in a  simplified
       version of the example above:

              paste <(cut -f1 file1) <(cut -f3 file2) > >(process)

       (note that no MULTIOS are involved), process will be run asynchronously
       as far as the parent shell is concerned.  The workaround is:

              { paste <(cut -f1 file1) <(cut -f3 file2) } > >(process)

       The extra processes here are spawned from the parent shell  which  will
       wait for their completion.

       Another problem arises any time a job with a substitution that requires
       a temporary file is disowned by the shell,  including  the  case  where
       `&!'  or `&|' appears at the end of a command containing a subsitution.
       In that case the temporary file will not be cleaned up as the shell  no
       longer  has  any memory of the job.  A workaround is to use a subshell,
       for example,

              (mycmd =(myoutput)) &!

       as the forked subshell will wait for the command to finish then  remove
       the temporary file.

       A  general  workaround  to ensure a process substitution endures for an
       appropriate length of time is to pass it as a parameter to an anonymous
       shell  function  (a  piece  of  shell code that is run immediately with
       function scope).  For example, this code:

              () {
                 print File $1:
                 cat $1
              } =(print This be the verse)

       outputs something resembling the following

              File /tmp/zsh6nU0kS:
              This be the verse

       The temporary file created by the process substitution will be  deleted
       when the function exits.



PARAMETER EXPANSION

       The  character `$' is used to introduce parameter expansions.  See zsh-
       param(1) for a description of parameters, including arrays, associative
       arrays, and subscript notation to access individual array elements.

       Note  in  particular the fact that words of unquoted parameters are not
       automatically split on whitespace unless the  option  SH_WORD_SPLIT  is
       set;  see references to this option below for more details.  This is an
       important difference from other shells.

       In the expansions discussed below that require a pattern, the  form  of
       the  pattern  is the same as that used for filename generation; see the
       section `Filename Generation'.  Note that these  patterns,  along  with
       the  replacement  text  of any substitutions, are themselves subject to
       parameter expansion, command substitution,  and  arithmetic  expansion.
       In  addition to the following operations, the colon modifiers described
       in the section `Modifiers' in the section `History  Expansion'  can  be
       applied:   for example, ${i:s/foo/bar/} performs string substitution on
       the expansion of parameter $i.

       ${name}
              The value, if any, of the parameter name  is  substituted.   The
              braces are required if the expansion is to be followed by a let-
              ter, digit, or underscore that is not to be interpreted as  part
              of  name.   In  addition, more complicated forms of substitution
              usually require the braces to be present; exceptions, which only
              apply  if  the  option  KSH_ARRAYS is not set, are a single sub-
              script or any colon modifiers appearing after the name,  or  any
              of the characters `^', `=', `~', `#' or `+' appearing before the
              name, all of which work with or without braces.

              If name is an array parameter, and the KSH_ARRAYS option is  not
              set,  then the value of each element of name is substituted, one
              element per word.  Otherwise, the expansion results in one  word
              only;  with  KSH_ARRAYS,  this is the first element of an array.
              No  field  splitting  is  done  on   the   result   unless   the
              SH_WORD_SPLIT   option  is  set.   See  also  the  flags  =  and
              s:string:.

       ${+name}
              If name is the name of a set parameter `1' is substituted,  oth-
              erwise `0' is substituted.

       ${name-word}
       ${name:-word}
              If  name is set, or in the second form is non-null, then substi-
              tute its value; otherwise substitute word.  In the  second  form
              name may be omitted, in which case word is always substituted.

       ${name+word}
       ${name:+word}
              If  name is set, or in the second form is non-null, then substi-
              tute word; otherwise substitute nothing.

       ${name=word}
       ${name:=word}
       ${name::=word}
              In the first form, if name is unset then set it to word; in  the
              second  form,  if name is unset or null then set it to word; and
              in the third form, unconditionally set name  to  word.   In  all
              forms, the value of the parameter is then substituted.

       ${name?word}
       ${name:?word}
              In the first form, if name is set, or in the second form if name
              is both set and non-null, then substitute its value;  otherwise,
              print  word and exit from the shell.  Interactive shells instead
              return to the prompt.  If word is omitted, then a standard  mes-
              sage is printed.

       In  any of the above expressions that test a variable and substitute an
       alternate word, note that you can use standard  shell  quoting  in  the
       word   value   to  selectively  override  the  splitting  done  by  the
       SH_WORD_SPLIT option and the = flag, but not splitting by the s:string:
       flag.

       In  the  following expressions, when name is an array and the substitu-
       tion is not quoted, or if the `(@)' flag or the name[@] syntax is used,
       matching and replacement is performed on each array element separately.

       ${name#pattern}
       ${name##pattern}
              If the pattern matches the beginning of the value of name,  then
              substitute  the  value of name with the matched portion deleted;
              otherwise, just substitute the value  of  name.   In  the  first
              form,  the smallest matching pattern is preferred; in the second
              form, the largest matching pattern is preferred.

       ${name%pattern}
       ${name%%pattern}
              If the pattern matches the end of the value of name,  then  sub-
              stitute the value of name with the matched portion deleted; oth-
              erwise, just substitute the value of name.  In the  first  form,
              the  smallest matching pattern is preferred; in the second form,
              the largest matching pattern is preferred.

       ${name:#pattern}
              If the pattern matches the value of name,  then  substitute  the
              empty  string; otherwise, just substitute the value of name.  If
              name is an array the matching array elements  are  removed  (use
              the `(M)' flag to remove the non-matched elements).

       ${name:|arrayname}
              If  arrayname is the name (N.B., not contents) of an array vari-
              able, then any elements contained in arrayname are removed  from
              the substitution of name.  If the substitution is scalar, either
              because name is a scalar variable or the expression  is  quoted,
              the  elements of arrayname are instead tested against the entire
              expression.

       ${name:*arrayname}
              Similar to the preceding subsitution, but in the opposite sense,
              so that entries present in both the original substitution and as
              elements of arrayname are retained and others removed.

       ${name:offset}
       ${name:offset:length}
              This syntax gives effects similar to parameter  subscripting  in
              the  form $name[start,end], but is compatible with other shells;
              note that both offset and  length  are  interpreted  differently
              from the components of a subscript.

              If offset is non-negative, then if the variable name is a scalar
              substitute the contents  starting  offset  characters  from  the
              first  character  of the string, and if name is an array substi-
              tute elements starting offset elements from the  first  element.
              If length is given, substitute that many characters or elements,
              otherwise the entire rest of the scalar or array.

              A positive offset is always treated as the offset of a character
              or  element  in  name from the first character or element of the
              array (this is different from native  zsh  subscript  notation).
              Hence  0  refers to the first character or element regardless of
              the setting of the option KSH_ARRAYS.

              A negative offset counts backwards from the end of the scalar or
              array,  so that -1 corresponds to the last character or element,
              and so on.

              When positive, length counts from the offset position toward the
              end  of  the scalar or array.  When negative, length counts back
              from the end.  If this results in a position smaller  than  off-
              set, a diagnostic is printed and nothing is substituted.

              The option MULTIBYTE is obeyed, i.e. the offset and length count
              multibyte characters where appropriate.

              offset and length undergo the same set of shell substitutions as
              for  scalar  assignment;  in  addition, they are then subject to
              arithmetic evaluation.  Hence, for example

                     print ${foo:3}
                     print ${foo: 1 + 2}
                     print ${foo:$(( 1 + 2))}
                     print ${foo:$(echo 1 + 2)}

              all have the same effect, extracting the string starting at  the
              fourth  character  of  $foo  if  the  substution would otherwise
              return a scalar, or the array starting at the fourth element  if
              $foo   would  return  an  array.   Note  that  with  the  option
              KSH_ARRAYS $foo always returns a scalar (regardless of  the  use
              of  the  offset syntax) and a form such as $foo[*]:3 is required
              to extract elements of an array named foo.

              If offset is negative, the - may not  appear  immediately  after
              the  : as this indicates the ${name:-word} form of substitution.
              Instead, a space may be inserted  before  the  -.   Furthermore,
              neither offset nor length may begin with an alphabetic character
              or & as these are used to indicate history-style modifiers.   To
              substitute  a value from a variable, the recommended approach is
              to precede it with a $ as this signifies the intention  (parame-
              ter substitution can easily be rendered unreadable); however, as
              arithmetic substitution  is  performed,  the  expression  ${var:
              offs} does work, retrieving the offset from $offs.

              For  further  compatibility with other shells there is a special
              case for array offset 0.  This usually  accesses  to  the  first
              element  of  the array.  However, if the substitution refers the
              positional parameter array, e.g. $@ or $*, then offset 0 instead
              refers to $0, offset 1 refers to $1, and so on.  In other words,
              the  positional  parameter  array  is  effectively  extended  by
              prepending  $0.  Hence ${*:0:1} substitutes $0 and ${*:1:1} sub-
              stitutes $1.

       ${name/pattern/repl}
       ${name//pattern/repl}
              Replace the longest possible match of pattern in  the  expansion
              of  parameter name by string repl.  The first form replaces just
              the first occurrence, the second  form  all  occurrences.   Both
              pattern  and  repl are subject to double-quoted substitution, so
              that expressions like ${name/$opat/$npat} will  work,  but  note
              the  usual rule that pattern characters in $opat are not treated
              specially unless either the option GLOB_SUBST is set,  or  $opat
              is instead substituted as ${~opat}.

              The pattern may begin with a `#', in which case the pattern must
              match at the start of the string, or `%', in which case it  must
              match  at  the end of the string, or `#%' in which case the pat-
              tern must match the entire string.  The repl  may  be  an  empty
              string,  in  which  case  the final `/' may also be omitted.  To
              quote the final `/' in other cases it should be  preceded  by  a
              single backslash; this is not necessary if the `/' occurs inside
              a substituted parameter.  Note also that the `#',  `%'  and  `#%
              are  not  active  if  they occur inside a substituted parameter,
              even at the start.

              The first `/' may be preceded by a `:', in which case the  match
              will  only succeed if it matches the entire word.  Note also the
              effect of the I and S parameter expansion flags below;  however,
              the flags M, R, B, E and N are not useful.

              For example,

                     foo="twinkle twinkle little star" sub="t*e" rep="spy"
                     print ${foo//${~sub}/$rep}
                     print ${(S)foo//${~sub}/$rep}

              Here, the `~' ensures that the text of $sub is treated as a pat-
              tern rather than a plain string.  In the first case, the longest
              match for t*e is substituted and the result is `spy star', while
              in the second case, the  shortest  matches  are  taken  and  the
              result is `spy spy lispy star'.

       ${#spec}
              If spec is one of the above substitutions, substitute the length
              in characters of the result instead of the  result  itself.   If
              spec  is  an array expression, substitute the number of elements
              of the result.  Note that `^', `=', and `~', below, must  appear
              to the left of `#' when these forms are combined.

       ${^spec}
              Turn  on  the RC_EXPAND_PARAM option for the evaluation of spec;
              if the `^' is doubled, turn it off.  When this  option  is  set,
              array expansions of the form foo${xx}bar, where the parameter xx
              is set to  (a  b  c),  are  substituted  with  `fooabar  foobbar
              foocbar'  instead  of  the  default `fooa b cbar'.  Note that an
              empty array will therefore cause all arguments to be removed.

              Internally, each such expansion is converted into the equivalent
              list    for    brace    expansion.     E.g.,   ${^var}   becomes
              {$var[1],$var[2],...}, and is processed as described in the sec-
              tion  `Brace  Expansion'  below.   If  word splitting is also in
              effect the $var[N] may themselves be split into  different  list
              elements.

       ${=spec}
              Perform  word splitting using the rules for SH_WORD_SPLIT during
              the evaluation of spec, but regardless of whether the  parameter
              appears  in  double  quotes; if the `=' is doubled, turn it off.
              This forces parameter expansions to be split into separate words
              before  substitution, using IFS as a delimiter.  This is done by
              default in most other shells.

              Note that splitting is applied to word in the  assignment  forms
              of  spec  before  the  assignment  to  name  is performed.  This
              affects the result of array assignments with the A flag.

       ${~spec}
              Turn on the GLOB_SUBST option for the evaluation of spec; if the
              `~'  is  doubled,  turn  it  off.   When this option is set, the
              string resulting from the expansion will  be  interpreted  as  a
              pattern anywhere that is possible, such as in filename expansion
              and filename generation and pattern-matching contexts  like  the
              right hand side of the `=' and `!=' operators in conditions.

              In  nested  substitutions, note that the effect of the ~ applies
              to the result of the current level of substitution.  A surround-
              ing  pattern  operation on the result may cancel it.  Hence, for
              example, if the parameter foo is set to  *,  ${~foo//\*/*.c}  is
              substituted  by  the pattern *.c, which may be expanded by file-
              name  generation,  but  ${${~foo}//\*/*.c}  substitutes  to  the
              string *.c, which will not be further expanded.

       If  a ${...} type parameter expression or a $(...) type command substi-
       tution is used in place of name above, it is  expanded  first  and  the
       result is used as if it were the value of name.  Thus it is possible to
       perform nested operations:  ${${foo#head}%tail} substitutes  the  value
       of  $foo  with both `head' and `tail' deleted.  The form with $(...) is
       often useful in combination with the  flags  described  next;  see  the
       examples  below.   Each  name or nested ${...} in a parameter expansion
       may also be followed by a subscript expression as  described  in  Array
       Parameters in zshparam(1).

       Note  that double quotes may appear around nested expressions, in which
       case  only  the  part  inside  is  treated  as  quoted;  for   example,
       ${(f)"$(foo)"}  quotes  the  result  of $(foo), but the flag `(f)' (see
       below) is applied using the rules for unquoted expansions.   Note  fur-
       ther that quotes are themselves nested in this context; for example, in
       "${(@f)"$(foo)"}", there are two sets of quotes,  one  surrounding  the
       whole  expression,  the  other  (redundant)  surrounding  the $(foo) as
       before.


   Parameter Expansion Flags
       If the opening brace is directly followed by  an  opening  parenthesis,
       the  string  up  to the matching closing parenthesis will be taken as a
       list of flags.  In cases where repeating a flag is meaningful, the rep-
       etitions need not be consecutive; for example, `(q%q%q)' means the same
       thing as the more readable `(%%qqq)'.  The  following  flags  are  sup-
       ported:

       #      Evaluate  the  resulting words as numeric expressions and output
              the characters corresponding to  the  resulting  integer.   Note
              that  this  form  is entirely distinct from use of the # without
              parentheses.

              If the MULTIBYTE option is set and the number  is  greater  than
              127  (i.e.  not  an  ASCII character) it is treated as a Unicode
              character.

       %      Expand all % escapes in the resulting words in the same  way  as
              in prompts (see EXPANSION OF PROMPT SEQUENCES in zshmisc(1)). If
              this flag is given twice, full prompt expansion is done  on  the
              resulting words, depending on the setting of the PROMPT_PERCENT,
              PROMPT_SUBST and PROMPT_BANG options.

       @      In double quotes, array elements are put  into  separate  words.
              E.g.,   `"${(@)foo}"'   is   equivalent   to  `"${foo[@]}"'  and
              `"${(@)foo[1,2]}"' is the same as `"$foo[1]"  "$foo[2]"'.   This
              is  distinct  from field splitting by the f, s or z flags, which
              still applies within each array element.

       A      Create an array parameter with  `${...=...}',  `${...:=...}'  or
              `${...::=...}'.   If  this flag is repeated (as in `AA'), create
              an associative array parameter.  Assignment is made before sort-
              ing  or  padding.   The name part may be a subscripted range for
              ordinary arrays; the word part must be converted  to  an  array,
              for example by using `${(AA)=name=...}' to activate field split-
              ting, when creating an associative array.

       a      Sort in array index  order;  when  combined  with  `O'  sort  in
              reverse  array  index order.  Note that `a' is therefore equiva-
              lent to the default but `Oa' is useful for obtaining an  array's
              elements in reverse order.

       c      With ${#name}, count the total number of characters in an array,
              as if the elements were concatenated with spaces between them.

       C      Capitalize the resulting words.  `Words' in this case refers  to
              sequences  of  alphanumeric characters separated by non-alphanu-
              merics, not to words that result from field splitting.

       D      Assume the string or  array  elements  contain  directories  and
              attempt  to  substitute the leading part of these by names.  The
              remainder of the path (the whole of it if the leading  part  was
              not  subsituted)  is then quoted so that the whole string can be
              used as a shell argument.  This is the reverse of `~'  substitu-
              tion:  see the section FILENAME EXPANSION below.

       e      Perform parameter expansion, command substitution and arithmetic
              expansion on the result. Such expansions can be nested  but  too
              deep recursion may have unpredictable effects.

       f      Split  the result of the expansion at newlines. This is a short-
              hand for `ps:\n:'.

       F      Join the words of arrays together using newline as a  separator.
              This is a shorthand for `pj:\n:'.

       g:opts:
              Process  escape  sequences like the echo builtin when no options
              are given (g::).  With the o option, octal escapes don't take  a
              leading  zero.   With the c option, sequences like `^X' are also
              processed.  With the e  option,  processes  `\M-t'  and  similar
              sequences  like  the  print  builtin.   With both of the o and e
              options, behaves like the print builtin except that in  none  of
              these modes is `\c' interpreted.

       i      Sort case-insensitively.  May be combined with `n' or `O'.

       k      If  name  refers  to  an  associative array, substitute the keys
              (element names) rather than the values of  the  elements.   Used
              with  subscripts  (including  ordinary arrays), force indices or
              keys to be substituted even if the subscript form refers to val-
              ues.   However,  this  flag  may  not be combined with subscript
              ranges.

       L      Convert all letters in the result to lower case.

       n      Sort decimal integers numerically; if the first differing  char-
              acters  of  two test strings are not digits, sorting is lexical.
              Integers with more initial zeroes are sorted before  those  with
              fewer  or  none.   Hence  the  array `foo1 foo02 foo2 foo3 foo20
              foo23' is sorted into the order shown.  May be combined with `i'
              or `O'.

       o      Sort  the resulting words in ascending order; if this appears on
              its own the sorting is lexical and  case-sensitive  (unless  the
              locale renders it case-insensitive).  Sorting in ascending order
              is the default for other forms of sorting, so this is ignored if
              combined with `a', `i' or `n'.

       O      Sort  the  resulting words in descending order; `O' without `a',
              `i' or `n' sorts in reverse lexical order.  May be combined with
              `a', `i' or `n' to reverse the order of sorting.

       P      This forces the value of the parameter name to be interpreted as
              a further parameter name, whose value will be used where  appro-
              priate.   Note  that flags set with one of the typeset family of
              commands (in particular case transformations) are not applied to
              the value of name used in this fashion.

              If  used  with  a  nested parameter or command substitution, the
              result of that will be taken as a parameter  name  in  the  same
              way.   For  example,  if  you  have `foo=bar' and `bar=baz', the
              strings ${(P)foo}, ${(P)${foo}}, and ${(P)$(echo bar)}  will  be
              expanded to `baz'.

       q      Quote  characters that are special to the shell in the resulting
              words with backslashes; unprintable or  invalid  characters  are
              quoted  using  the  $'\NNN'  form, with separate quotes for each
              octet.

              If this flag is given twice, the resulting words are  quoted  in
              single  quotes  and  if  it  is given three times, the words are
              quoted in double quotes; in these forms no special  handling  of
              unprintable  or invalid characters is attempted.  If the flag is
              given four times, the words are quoted in single quotes preceded
              by  a  $.  Note that in all three of these forms quoting is done
              unconditionally, even if  this  does  not  change  the  way  the
              resulting string would be interpreted by the shell.

              If a q- is given (only a single q may appear), a minimal form of
              single quoting is used that only quotes the string if needed  to
              protect  special characters.  Typically this form gives the most
              readable output.

       Q      Remove one level of quotes from the resulting words.

       t      Use a string describing the type  of  the  parameter  where  the
              value  of  the  parameter would usually appear. This string con-
              sists of keywords separated by hyphens (`-'). The first  keyword
              in  the  string  describes  the  main  type,  it  can  be one of
              `scalar', `array',  `integer',  `float'  or  `association'.  The
              other keywords describe the type in more detail:

              local  for local parameters

              left   for left justified parameters

              right_blanks
                     for right justified parameters with leading blanks

              right_zeros
                     for right justified parameters with leading zeros

              lower  for parameters whose value is converted to all lower case
                     when it is expanded

              upper  for parameters whose value is converted to all upper case
                     when it is expanded

              readonly
                     for readonly parameters

              tag    for tagged parameters

              export for exported parameters

              unique for arrays which keep only the first occurrence of dupli-
                     cated values

              hide   for parameters with the `hide' flag

              special
                     for special parameters defined by the shell

       u      Expand only the first occurrence of each unique word.

       U      Convert all letters in the result to upper case.

       v      Used with k, substitute (as two consecutive words) both the  key
              and the value of each associative array element.  Used with sub-
              scripts, force values to be substituted even  if  the  subscript
              form refers to indices or keys.

       V      Make any special characters in the resulting words visible.

       w      With  ${#name}, count words in arrays or strings; the s flag may
              be used to set a word delimiter.

       W      Similar to w  with  the  difference  that  empty  words  between
              repeated delimiters are also counted.

       X      With  this  flag,  parsing  errors occurring with the Q, e and #
              flags or the pattern matching forms  such  as  `${name#pattern}'
              are reported.  Without the flag, errors are silently ignored.

       z      Split the result of the expansion into words using shell parsing
              to find the words, i.e. taking into account any quoting  in  the
              value.   Comments  are  not  treated  specially  but as ordinary
              strings, similar to interactive shells with the INTERACTIVE_COM-
              MENTS  option  unset  (however, see the Z flag below for related
              options)

              Note that this is done very late,  even  later  than  the  `(s)'
              flag.  So to access single words in the result use nested expan-
              sions as in `${${(z)foo}[2]}'. Likewise, to remove the quotes in
              the resulting words use `${(Q)${(z)foo}}'.

       0      Split  the  result  of  the  expansion on null bytes.  This is a
              shorthand for `ps:\0:'.

       The following flags (except p) are followed by one or more arguments as
       shown.  Any character, or the matching pairs `(...)', `{...}', `[...]',
       or `<...>', may be used in place of a colon  as  delimiters,  but  note
       that when a flag takes more than one argument, a matched pair of delim-
       iters must surround each argument.

       p      Recognize the same escape sequences  as  the  print  builtin  in
              string arguments to any of the flags described below that follow
              this argument.

       ~      Force string arguments to any of the  flags  below  that  follow
              within  the parentheses to be treated as patterns.  Compare with
              a ~ outside parentheses, which  forces  the  entire  substituted
              string to be treated as a pattern.  Hence, for example,
              [[ "?" = ${(~j.|.)array} ]]
       with  the  EXTENDED_GLOB option set succeeds if and only if $array con-
       tains the string `?' as an element.  The argument may  be  repeated  to
       toggle the behaviour; its effect only lasts to the end of the parenthe-
       sised group.

       j:string:
              Join the words of arrays together using string as  a  separator.
              Note  that  this  occurs before field splitting by the s:string:
              flag or the SH_WORD_SPLIT option.

       l:expr::string1::string2:
              Pad the resulting words on the left.  Each word  will  be  trun-
              cated if required and placed in a field expr characters wide.

              The arguments :string1: and :string2: are optional; neither, the
              first, or both may be given.  Note that the same pairs of delim-
              iters  must  be used for each of the three arguments.  The space
              to the left will be filled with string1 (concatenated  as  often
              as  needed)  or spaces if string1 is not given.  If both string1
              and string2 are given, string2 is inserted once directly to  the
              left  of  each  word,  truncated if necessary, before string1 is
              used to produce any remaining padding.

              If the MULTIBYTE option is in effect, the flag  m  may  also  be
              given,  in which case widths will be used for the calculation of
              padding; otherwise individual multibyte characters  are  treated
              as occupying one unit of width.

              If  the  MULTIBYTE  option  is  not  in effect, each byte in the
              string is treated as occupying one unit of width.

              Control characters are always assumed to be one unit wide;  this
              allows  the  mechanism  to be used for generating repetitions of
              control characters.

       m      Only useful together with one of the flags l or r or with the  #
              length operator when the MULTIBYTE option is in effect.  Use the
              character width reported by the system in calculating  how  much
              of  the  string it occupies or the overall length of the string.
              Most printable characters have a width of one unit, however cer-
              tain  Asian character sets and certain special effects use wider
              characters; combining characters have zero width.  Non-printable
              characters are arbitrarily counted as zero width; how they would
              actually be displayed will vary.

              If the m is repeated, the character either counts  zero  (if  it
              has zero width), else one.  For printable character strings this
              has the effect of counting the number of glyphs  (visibly  sepa-
              rate characters), except for the case where combining characters
              themselves have non-zero width (true in certain alphabets).

       r:expr::string1::string2:
              As l, but pad the words on the right and insert string2  immedi-
              ately to the right of the string to be padded.

              Left  and  right padding may be used together.  In this case the
              strategy is to apply left padding to the  first  half  width  of
              each  of  the  resulting  words, and right padding to the second
              half.  If the string to be padded has odd width the  extra  pad-
              ding is applied on the left.

       s:string:
              Force  field  splitting  at  the  separator string.  Note that a
              string of two or more characters means that  all  of  them  must
              match  in  sequence;  this  differs from the treatment of two or
              more characters in the IFS parameter.  See also the =  flag  and
              the  SH_WORD_SPLIT option.  An empty string may also be given in
              which case every character will be a separate element.

              For historical reasons, the usual  behaviour  that  empty  array
              elements  are  retained  inside  double  quotes  is disabled for
              arrays generated by splitting; hence the following:

                     line="one::three"
                     print -l "${(s.:.)line}"

              produces two lines of output for one and three  and  elides  the
              empty  field.  To override this behaviour, supply the "(@)" flag
              as well, i.e.  "${(@s.:.)line}".

       Z:opts:
              As z but takes a combination of option letters between a follow-
              ing pair of delimiter characters.  With no options the effect is
              identical to z.  (Z+c+) causes comments to be parsed as a string
              and retained; any field in the resulting array beginning with an
              unquoted comment character is a comment.  (Z+C+) causes comments
              to  be  parsed  and removed.  The rule for comments is standard:
              anything between a word starting with  the  third  character  of
              $HISTCHARS,  default  #,  up  to  the next newline is a comment.
              (Z+n+) causes unquoted newlines to be treated as ordinary white-
              space,  else  they  are treated as if they are shell code delim-
              iters and converted to semicolons.  Options are combined  within
              the same set of delimiters, e.g. (Z+Cn+).

       _:flags:
              The  underscore (_) flag is reserved for future use.  As of this
              revision of zsh, there are no valid flags; anything following an
              underscore,  other  than an empty pair of delimiters, is treated
              as an error, and the flag itself has no effect.

       The following flags are meaningful with the  ${...#...}  or  ${...%...}
       forms.  The S and I flags may also be used with the ${.../...} forms.

       S      Search  substrings  as  well as beginnings or ends; with # start
              from the beginning and with % start from the end of the  string.
              With  substitution  via  ${.../...}  or  ${...//...},  specifies
              non-greedy matching, i.e. that the shortest instead of the long-
              est match should be replaced.

       I:expr:
              Search  the  exprth  match  (where  expr evaluates to a number).
              This only applies when searching for substrings, either with the
              S  flag,  or  with  ${.../...} (only the exprth match is substi-
              tuted) or ${...//...} (all matches from the exprth on  are  sub-
              stituted).  The default is to take the first match.

              The  exprth  match  is  counted such that there is either one or
              zero matches from each starting position in the string, although
              for  global  substitution  matches overlapping previous replace-
              ments are ignored.  With the ${...%...} and  ${...%%...}  forms,
              the starting position for the match moves backwards from the end
              as the index increases, while with the other forms it moves for-
              ward from the start.

              Hence with the string
                     which switch is the right switch for Ipswich?
              substitutions  of  the form ${(SI:N:)string#w*ch} as N increases
              from 1 will match  and  remove  `which',  `witch',  `witch'  and
              `wich';  the form using `##' will match and remove `which switch
              is the right switch for Ipswich', `witch is the right switch for
              Ipswich',  `witch  for  Ipswich'  and `wich'. The form using `%'
              will remove the same matches as for `#', but in  reverse  order,
              and the form using `%%' will remove the same matches as for `##'
              in reverse order.

       B      Include the index of the beginning of the match in the result.

       E      Include the index of the end of the match in the result.

       M      Include the matched portion in the result.

       N      Include the length of the match in the result.

       R      Include the unmatched portion in the result (the Rest).


   Rules
       Here is a summary of the rules  for  substitution;  this  assumes  that
       braces are present around the substitution, i.e. ${...}.  Some particu-
       lar examples are given below.  Note  that  the  Zsh  Development  Group
       accepts  no  responsibility for any brain damage which may occur during
       the reading of the following rules.

       1. Nested substitution
              If multiple nested ${...} forms  are  present,  substitution  is
              performed  from the inside outwards.  At each level, the substi-
              tution takes account of whether the current value is a scalar or
              an  array,  whether  the whole substitution is in double quotes,
              and what flags are supplied to the current  level  of  substitu-
              tion,  just  as  if  the nested substitution were the outermost.
              The flags are not propagated up to enclosing substitutions;  the
              nested  substitution  will return either a scalar or an array as
              determined by the flags, possibly adjusted for quoting.  All the
              following  steps  take  place  where applicable at all levels of
              substitution.  Note that, unless the `(P)' flag is present,  the
              flags  and  any  subscripts  apply  directly to the value of the
              nested  substitution;  for  example,  the  expansion   ${${foo}}
              behaves exactly the same as ${foo}.

              At  each  nested  level  of  substitution, the substituted words
              undergo all forms of single-word substitution (i.e. not filename
              generation),  including  command substitution, arithmetic expan-
              sion and filename expansion (i.e. leading ~ and =).   Thus,  for
              example,  ${${:-=cat}:h}  expands to the directory where the cat
              program resides.  (Explanation: the internal substitution has no
              parameter  but  a default value =cat, which is expanded by file-
              name expansion to a  full  path;  the  outer  substitution  then
              applies  the  modifier  :h  and  takes the directory part of the
              path.)

       2. Internal parameter flags
              Any parameter flags set by one of the  typeset  family  of  com-
              mands,  in particular the L, R, Z, u and l flags for padding and
              capitalization, are applied directly  to  the  parameter  value.
              Note  these flags are options to the command, e.g. `typeset -Z';
              they are not the same as the flags used within parameter substi-
              tutions.

       3. Parameter subscripting
              If the value is a raw parameter reference with a subscript, such
              as ${var[3]}, the effect of subscripting is applied directly  to
              the  parameter.   Subscripts are evaluated left to right; subse-
              quent subscripts apply to the scalar or array value  yielded  by
              the  previous  subscript.  Thus if var is an array, ${var[1][2]}
              is the second character of the first word, but ${var[2,4][2]} is
              the entire third word (the second word of the range of words two
              through four of the original array).  Any number  of  subscripts
              may appear.

       4. Parameter name replacement
              The  effect  of any (P) flag, which treats the value so far as a
              parameter name and replaces it with the corresponding value,  is
              applied.

       5. Double-quoted joining
              If  the  value after this process is an array, and the substitu-
              tion appears in double quotes, and no (@) flag is present at the
              current  level, the words of the value are joined with the first
              character of the parameter $IFS, by  default  a  space,  between
              each  word  (single  word  arrays are not modified).  If the (j)
              flag is present, that is used for joining instead of $IFS.

       6. Nested subscripting
              Any remaining subscripts (i.e. of  a  nested  substitution)  are
              evaluated  at this point, based on whether the value is an array
              or a scalar.  As with 3., multiple subscripts can appear.   Note
              that  ${foo[2,4][2]} is thus equivalent to ${${foo[2,4]}[2]} and
              also to "${${(@)foo[2,4]}[2]}" (the nested substitution  returns
              an  array  in  both  cases), but not to "${${foo[2,4]}[2]}" (the
              nested substitution returns a scalar because of the quotes).

       7. Modifiers
              Any modifiers, as specified by a trailing `#', `%', `/'  (possi-
              bly  doubled) or by a set of modifiers of the form :... (see the
              section `Modifiers' in the  section  `History  Expansion'),  are
              applied to the words of the value at this level.

       8. Character evaluation
              Any  (#)  flag  is applied, evaluating the result so far numeri-
              cally as a character.

       9. Length
              Any initial # modifier, i.e. in the form  ${#var},  is  used  to
              evaluate the length of the expression so far.

       10. Forced joining
              If  the  `(j)'  flag is present, or no `(j)' flag is present but
              the string is to be split as given by rule 11., and joining  did
              not  take  place  at  step 5., any words in the value are joined
              together using the given string or the first character  of  $IFS
              if  none.  Note that the `(F)' flag implicitly supplies a string
              for joining in this manner.

       11. Simple word splitting
              If one of the `(s)' or `(f)' flags are present, or the `=' spec-
              ifier  was  present  (e.g. ${=var}), the word is split on occur-
              rences of the specified string, or (for = with  neither  of  the
              two flags present) any of the characters in $IFS.

              If  no `(s)', `(f)' or `=' was given, but the word is not quoted
              and the option SH_WORD_SPLIT is set, the word is split on occur-
              rences  of  any of the characters in $IFS.  Note this step, too,
              takes place at all levels of a nested substitution.

       12. Case modification
              Any case modification from one of the flags (L), (U) or  (C)  is
              applied.

       13. Escape sequence replacement
              First any replacements from the (g) flag are performed, then any
              prompt-style formatting from the (%) family of flags is applied.

       14. Quote application
              Any  quoting or unquoting using (q) and (Q) and related flags is
              applied.

       15. Directory naming
              Any directory name substitution using (D) flag is applied.

       16. Visibility enhancement
              Any modifications to make characters visible using the (V)  flag
              are applied.

       17. Lexical word splitting
              If  the  '(z)'  flag  or  one  of the forms of the '(Z)' flag is
              present, the word is split as if it were a shell  command  line,
              so  that  quotation  marks  and other metacharacters are used to
              decide what constitutes a word.  Note this form of splitting  is
              entirely  distinct  from that described by rule 11.: it does not
              use $IFS, and does not cause forced joining.

       18. Uniqueness
              If the result is an array and the `(u)' flag was present, dupli-
              cate elements are removed from the array.

       19. Ordering
              If  the  result  is still an array and one of the `(o)' or `(O)'
              flags was present, the array is reordered.

       20. Re-evaluation
              Any `(e)' flag is  applied  to  the  value,  forcing  it  to  be
              re-examined  for  new parameter substitutions, but also for com-
              mand and arithmetic substitutions.

       21. Padding
              Any padding of the value by the `(l.fill.)' or `(r.fill.)' flags
              is applied.

       22. Semantic joining
              In  contexts where expansion semantics requires a single word to
              result, all words are rejoined with the first character  of  IFS
              between.   So  in  `${(P)${(f)lines}}'  the value of ${lines} is
              split at newlines, but then must be joined again  before  the  P
              flag can be applied.

              If a single word is not required, this rule is skipped.

       23. Empty argument removal
              If  the  substitution  does  not  appear  in  double quotes, any
              resulting zero-length argument, whether from a scalar or an ele-
              ment  of an array, is elided from the list of arguments inserted
              into the command line.

              Strictly speaking, the removal happens later as the same happens
              with other forms of substitution; the point to note here is sim-
              ply that it occurs after any of the above parameter  operations.


   Examples
       The  flag  f  is  useful  to split a double-quoted substitution line by
       line.  For example, ${(f)"$(<file)"} substitutes the contents  of  file
       divided  so  that each line is an element of the resulting array.  Com-
       pare this with the effect of $(<file) alone, which divides the file  up
       by words, or the same inside double quotes, which makes the entire con-
       tent of the file a single string.

       The following illustrates the rules for  nested  parameter  expansions.
       Suppose that $foo contains the array (bar baz):

       "${(@)${foo}[1]}"
              This  produces  the  result  b.   First,  the inner substitution
              "${foo}", which has no array (@) flag, produces  a  single  word
              result "bar baz".  The outer substitution "${(@)...[1]}" detects
              that this is a scalar, so that (despite the `(@)' flag) the sub-
              script picks the first character.

       "${${(@)foo}[1]}"
              This produces the result `bar'.  In this case, the inner substi-
              tution "${(@)foo}" produces the array `(bar  baz)'.   The  outer
              substitution "${...[1]}" detects that this is an array and picks
              the first word.  This is similar to the simple case "${foo[1]}".

       As an example of the rules for word splitting and joining, suppose $foo
       contains the array `(ax1 bx1)'.  Then

       ${(s/x/)foo}
              produces the words `a', `1 b' and `1'.

       ${(j/x/s/x/)foo}
              produces `a', `1', `b' and `1'.

       ${(s/x/)foo%%1*}
              produces `a' and ` b' (note the extra space).   As  substitution
              occurs  before either joining or splitting, the operation  first
              generates the modified array (ax bx), which is  joined  to  give
              "ax  bx",  and  then  split to give `a', ` b' and `'.  The final
              empty string will then be elided, as it is not in double quotes.



COMMAND SUBSTITUTION

       A  command  enclosed  in  parentheses  preceded  by a dollar sign, like
       `$(...)', or quoted with grave accents, like ``...`', is replaced  with
       its  standard  output, with any trailing newlines deleted.  If the sub-
       stitution is not enclosed in double quotes, the output is  broken  into
       words  using  the  IFS parameter.  The substitution `$(cat foo)' may be
       replaced by the equivalent but faster `$(<foo)'.  In  either  case,  if
       the  option GLOB_SUBST is set, the output is eligible for filename gen-
       eration.


ARITHMETIC EXPANSION

       A string of the form `$[exp]' or `$((exp))'  is  substituted  with  the
       value  of the arithmetic expression exp.  exp is subjected to parameter
       expansion, command substitution and arithmetic expansion before  it  is
       evaluated.  See the section `Arithmetic Evaluation'.


BRACE EXPANSION

       A  string  of the form `foo{xx,yy,zz}bar' is expanded to the individual
       words `fooxxbar', `fooyybar' and `foozzbar'.   Left-to-right  order  is
       preserved.   This  construct  may  be  nested.  Commas may be quoted in
       order to include them literally in a word.

       An expression of the form `{n1..n2}', where n1 and n2 are integers,  is
       expanded to every number between n1 and n2 inclusive.  If either number
       begins with a zero, all the resulting numbers will be padded with lead-
       ing  zeroes to that minimum width, but for negative numbers the - char-
       acter is also included in the width.  If the numbers are in  decreasing
       order the resulting sequence will also be in decreasing order.

       An  expression  of  the  form  `{n1..n2..n3}', where n1, n2, and n3 are
       integers, is expanded as above, but only  every  n3th  number  starting
       from n1 is output.  If n3 is negative the numbers are output in reverse
       order, this is slightly different from simply swapping n1 and n2 in the
       case  that  the  step n3 doesn't evenly divide the range.  Zero padding
       can be specified in any of the three  numbers,  specifying  it  in  the
       third  can  be  useful to pad for example `{-99..100..01}' which is not
       possible to specify by putting a 0 on either of the first  two  numbers
       (i.e. pad to two characters).

       If  a  brace  expression  matches  none  of the above forms, it is left
       unchanged, unless the option  BRACE_CCL  (an  abbreviation  for  `brace
       character  class')  is  set.  In that case, it is expanded to a list of
       the individual characters between the braces sorted into the  order  of
       the characters in the ASCII character set (multibyte characters are not
       currently handled).  The syntax is similar to  a  [...]  expression  in
       filename  generation:  `-'  is  treated  specially to denote a range of
       characters, but `^' or `!' as the first character is treated  normally.
       For  example, `{abcdef0-9}' expands to 16 words 0 1 2 3 4 5 6 7 8 9 a b
       c d e f.

       Note that brace expansion is not part  of  filename  generation  (glob-
       bing);  an  expression  such  as */{foo,bar} is split into two separate
       words */foo and */bar before filename generation takes place.  In  par-
       ticular,  note  that  this  is  liable to produce a `no match' error if
       either of the two expressions does not match; this is to be  contrasted
       with  */(foo|bar),  which  is treated as a single pattern but otherwise
       has similar effects.

       To combine brace expansion with array expansion, see the ${^spec}  form
       described in the section Parameter Expansion above.



FILENAME EXPANSION

       Each  word  is checked to see if it begins with an unquoted `~'.  If it
       does, then the word up to a `/', or the end of the word if there is  no
       `/',  is  checked  to  see  if it can be substituted in one of the ways
       described here.  If so, then  the  `~'  and  the  checked  portion  are
       replaced with the appropriate substitute value.

       A `~' by itself is replaced by the value of $HOME.  A `~' followed by a
       `+' or a `-' is replaced by  current  or  previous  working  directory,
       respectively.

       A  `~'  followed by a number is replaced by the directory at that posi-
       tion in the directory stack.  `~0' is equivalent to `~+', and  `~1'  is
       the  top  of  the  stack.  `~+' followed by a number is replaced by the
       directory at that position in the directory stack.  `~+0' is equivalent
       to  `~+', and `~+1' is the top of the stack.  `~-' followed by a number
       is replaced by the directory that many positions from the bottom of the
       stack.   `~-0'  is  the  bottom  of  the stack.  The PUSHD_MINUS option
       exchanges the effects of `~+' and `~-' where they  are  followed  by  a
       number.


   Dynamic named directories
       If  the  function  zsh_directory_name  exists,  or  the  shell variable
       zsh_directory_name_functions exists and contains an array  of  function
       names,  then the functions are used to implement dynamic directory nam-
       ing.  The functions are tried in order until one returns  status  zero,
       so it is important that functions test whether they can handle the case
       in question and return an appropriate status.

       A `~' followed by a  string  namstr  in  unquoted  square  brackets  is
       treated  specially  as  a  dynamic directory name.  Note that the first
       unquoted closing square bracket always terminates  namstr.   The  shell
       function  is  passed two arguments: the string n (for name) and namstr.
       It should either set the array reply to a single element which  is  the
       directory  corresponding  to the name and return status zero (executing
       an assignment as the last  statement  is  usually  sufficient),  or  it
       should return status non-zero.  In the former case the element of reply
       is used as the directory; in the latter case the substitution is deemed
       to  have  failed.  If all functions fail and the option NOMATCH is set,
       an error results.

       The functions defined as above are also used to see if a directory  can
       be turned into a name, for example when printing the directory stack or
       when expanding %~ in prompts.  In this case each function is passed two
       arguments:  the  string d (for directory) and the candidate for dynamic
       naming.  The function should either  return  non-zero  status,  if  the
       directory  cannot  be named by the function, or it should set the array
       reply to consist of two elements: the first is the dynamic name for the
       directory (as would appear within `~[...]'), and the second is the pre-
       fix length of the directory to be replaced.  For example, if the  trial
       directory   is   /home/myname/src/zsh   and   the   dynamic   name  for
       /home/myname/src (which has 16 characters) is s, then the function sets

              reply=(s 16)

       The  directory  name so returned is compared with possible static names
       for parts of the directory path, as described below; it is used if  the
       prefix  length  matched (16 in the example) is longer than that matched
       by any static name.

       It is not a requirement that a function implements both n and d  calls;
       for  example,  it  might  be  appropriate  for certain dynamic forms of
       expansion not to be contracted to names.  In that case  any  call  with
       the first argument d should cause a non-zero status to be returned.

       The  completion system calls `zsh_directory_name c' followed by equiva-
       lent calls to elements of the array zsh_directory_name_functions, if it
       exists,  in  order to complete dynamic names for directories.  The code
       for this should be as for any other completion function as described in
       zshcompsys(1).

       As a working example, here is a function that expands any dynamic names
       beginning with the string p: to directories  below  /home/pws/perforce.
       In  this  simple  case a static name for the directory would be just as
       effective.

              zsh_directory_name() {
                emulate -L zsh
                setopt extendedglob
                local -a match mbegin mend
                if [[ $1 = d ]]; then
                  # turn the directory into a name
                  if [[ $2 = (#b)(/home/pws/perforce/)([^/]##)* ]]; then
                    typeset -ga reply
                    reply=(p:$match[2] $(( ${#match[1]} + ${#match[2]} )) )
                  else
                    return 1
                  fi
                elif [[ $1 = n ]]; then
                  # turn the name into a directory
                  [[ $2 != (#b)p:(?*) ]] && return 1
                  typeset -ga reply
                  reply=(/home/pws/perforce/$match[1])
                elif [[ $1 = c ]]; then
                  # complete names
                  local expl
                  local -a dirs
                  dirs=(/home/pws/perforce/*(/:t))
                  dirs=(p:${^dirs})
                  _wanted dynamic-dirs expl 'dynamic directory' compadd -S\] -a dirs
                  return
                else
                  return 1
                fi
                return 0
              }


   Static named directories
       A `~' followed by anything not already covered consisting of any number
       of  alphanumeric  characters  or underscore (`_'), hyphen (`-'), or dot
       (`.') is looked up as a named directory, and replaced by the  value  of
       that  named  directory  if found.  Named directories are typically home
       directories for users on the system.  They may also be defined  if  the
       text  after the `~' is the name of a string shell parameter whose value
       begins with a `/'.  Note that trailing slashes will be removed from the
       path  to the directory (though the original parameter is not modified).

       It is also possible to define directory names using the  -d  option  to
       the hash builtin.

       In  certain  circumstances  (in  prompts, for instance), when the shell
       prints a path, the path is checked to see if it has a  named  directory
       as  its  prefix.  If so, then the prefix portion is replaced with a `~'
       followed by the name of the directory.  The shortest way  of  referring
       to  the  directory is used, with ties broken in favour of using a named
       directory, except when the directory is / itself.  The parameters  $PWD
       and $OLDPWD are never abbreviated in this fashion.


   `=' expansion
       If a word begins with an unquoted `=' and the EQUALS option is set, the
       remainder of the word is taken as the name of a command.  If a  command
       exists  by  that name, the word is replaced by the full pathname of the
       command.


   Notes
       Filename expansion is performed on the right hand side of  a  parameter
       assignment,  including  those  appearing  after commands of the typeset
       family.  In this case, the  right  hand  side  will  be  treated  as  a
       colon-separated list in the manner of the PATH parameter, so that a `~'
       or an `=' following a `:' is eligible for expansion.  All  such  behav-
       iour  can be disabled by quoting the `~', the `=', or the whole expres-
       sion (but not simply the colon); the EQUALS option is also respected.

       If the option MAGIC_EQUAL_SUBST is set, any unquoted shell argument  in
       the form `identifier=expression' becomes eligible for file expansion as
       described in the  previous  paragraph.   Quoting  the  first  `='  also
       inhibits this.



FILENAME GENERATION

       If  a  word contains an unquoted instance of one of the characters `*',
       `(', `|', `<', `[', or `?', it is regarded as a  pattern  for  filename
       generation,  unless  the  GLOB  option  is unset.  If the EXTENDED_GLOB
       option is set, the `^' and `#' characters also denote a pattern; other-
       wise they are not treated specially by the shell.

       The  word  is  replaced  with a list of sorted filenames that match the
       pattern.  If no matching pattern is found, the  shell  gives  an  error
       message,  unless the NULL_GLOB option is set, in which case the word is
       deleted; or unless the NOMATCH option is unset, in which case the  word
       is left unchanged.

       In  filename  generation, the character `/' must be matched explicitly;
       also, a `.' must be matched explicitly at the beginning of a pattern or
       after  a  `/', unless the GLOB_DOTS option is set.  No filename genera-
       tion pattern matches the files `.' or `..'.  In other instances of pat-
       tern matching, the `/' and `.' are not treated specially.

   Glob Operators
       *      Matches any string, including the null string.

       ?      Matches any character.

       [...]  Matches  any  of  the enclosed characters.  Ranges of characters
              can be specified by separating two characters by a `-'.   A  `-'
              or  `]' may be matched by including it as the first character in
              the list.  There are also several named classes  of  characters,
              in  the  form `[:name:]' with the following meanings.  The first
              set use the macros provided by the operating system to test  for
              the  given  character  combinations, including any modifications
              due to local language settings, see ctype(3):

              [:alnum:]
                     The character is alphanumeric

              [:alpha:]
                     The character is alphabetic

              [:ascii:]
                     The character is 7-bit, i.e. is a  single-byte  character
                     without the top bit set.

              [:blank:]
                     The character is either space or tab

              [:cntrl:]
                     The character is a control character

              [:digit:]
                     The character is a decimal digit

              [:graph:]
                     The  character is a printable character other than white-
                     space

              [:lower:]
                     The character is a lowercase letter

              [:print:]
                     The character is printable

              [:punct:]
                     The character is printable but neither  alphanumeric  nor
                     whitespace

              [:space:]
                     The character is whitespace

              [:upper:]
                     The character is an uppercase letter

              [:xdigit:]
                     The character is a hexadecimal digit

              Another  set of named classes is handled internally by the shell
              and is not sensitive to the locale:

              [:IDENT:]
                     The character is allowed to form part of a shell  identi-
                     fier, such as a parameter name

              [:IFS:]
                     The  character  is used as an input field separator, i.e.
                     is contained in the IFS parameter

              [:IFSSPACE:]
                     The character is an IFS white space  character;  see  the
                     documentation for IFS in the zshparam(1) manual page.

              [:WORD:]
                     The  character is treated as part of a word; this test is
                     sensitive to the value of the WORDCHARS parameter

              Note that the square brackets are additional to those  enclosing
              the  whole  set  of characters, so to test for a single alphanu-
              meric character you need `[[:alnum:]]'.   Named  character  sets
              can be used alongside other types, e.g. `[[:alpha:]0-9]'.

       [^...]
       [!...] Like [...], except that it matches any character which is not in
              the given set.

       <[x]-[y]>
              Matches any number in the range x to y,  inclusive.   Either  of
              the  numbers  may be omitted to make the range open-ended; hence
              `<->' matches any number.  To match individual digits, the [...]
              form is more efficient.

              Be  careful  when  using other wildcards adjacent to patterns of
              this form; for example, <0-9>* will actually  match  any  number
              whatsoever  at  the  start of the string, since the `<0-9>' will
              match the first digit, and the `*' will match any others.   This
              is  a  trap  for the unwary, but is in fact an inevitable conse-
              quence of the rule that the longest possible match  always  suc-
              ceeds.   Expressions  such  as  `<0-9>[^[:digit:]]*' can be used
              instead.

       (...)  Matches the enclosed pattern.  This is used  for  grouping.   If
              the  KSH_GLOB  option  is  set, then a `@', `*', `+', `?' or `!'
              immediately preceding the `(' is treated specially, as  detailed
              below.  The  option SH_GLOB prevents bare parentheses from being
              used in this way, though the KSH_GLOB option is still available.

              Note  that  grouping cannot extend over multiple directories: it
              is an error to have a `/' within a group (this only applies  for
              patterns  used in filename generation).  There is one exception:
              a group of the form (pat/)# appearing as a complete path segment
              can match a sequence of directories.  For example, foo/(a*/)#bar
              matches foo/bar, foo/any/bar, foo/any/anyother/bar, and so on.

       x|y    Matches either x or y.  This operator has lower precedence  than
              any  other.   The  `|'  character must be within parentheses, to
              avoid interpretation as a pipeline.

       ^x     (Requires EXTENDED_GLOB to be set.)  Matches anything except the
              pattern x.  This has a higher precedence than `/', so `^foo/bar'
              will search directories in `.' except `./foo' for a  file  named
              `bar'.

       x~y    (Requires EXTENDED_GLOB to be set.)  Match anything that matches
              the pattern x but does not match y.  This has  lower  precedence
              than  any  operator except `|', so `*/*~foo/bar' will search for
              all files in all directories in `.'  and then exclude  `foo/bar'
              if there was such a match.  Multiple patterns can be excluded by
              `foo~bar~baz'.  In the exclusion pattern (y), `/'  and  `.'  are
              not treated specially the way they usually are in globbing.

       x#     (Requires EXTENDED_GLOB to be set.)  Matches zero or more occur-
              rences of the pattern x.  This  operator  has  high  precedence;
              `12#'  is  equivalent to `1(2#)', rather than `(12)#'.  It is an
              error for an unquoted `#' to follow something  which  cannot  be
              repeated;  this includes an empty string, a pattern already fol-
              lowed by `##', or parentheses when part of  a  KSH_GLOB  pattern
              (for  example,  `!(foo)#'  is  invalid  and  must be replaced by
              `*(!(foo))').

       x##    (Requires EXTENDED_GLOB to be set.)  Matches one or more  occur-
              rences  of  the  pattern  x.  This operator has high precedence;
              `12##' is equivalent to `1(2##)', rather than `(12)##'.  No more
              than  two  active `#' characters may appear together.  (Note the
              potential clash with glob qualifiers in the form `1(2##)'  which
              should therefore be avoided.)

   ksh-like Glob Operators
       If  the KSH_GLOB option is set, the effects of parentheses can be modi-
       fied by a preceding `@', `*', `+', `?' or `!'.  This character need not
       be unquoted to have special effects, but the `(' must be.

       @(...) Match the pattern in the parentheses.  (Like `(...)'.)

       *(...) Match any number of occurrences.  (Like `(...)#'.)

       +(...) Match at least one occurrence.  (Like `(...)##'.)

       ?(...) Match zero or one occurrence.  (Like `(|...)'.)

       !(...) Match   anything  but  the  expression  in  parentheses.   (Like
              `(^(...))'.)

   Precedence
       The precedence of the operators given above is (highest) `^', `/', `~',
       `|'  (lowest);  the remaining operators are simply treated from left to
       right as part of a string, with `#' and `##' applying to  the  shortest
       possible  preceding unit (i.e. a character, `?', `[...]', `<...>', or a
       parenthesised expression).  As mentioned above, a `/' used as a  direc-
       tory  separator  may not appear inside parentheses, while a `|' must do
       so; in patterns used in other contexts than  filename  generation  (for
       example,  in  case statements and tests within `[[...]]'), a `/' is not
       special; and `/' is also not special  after  a  `~'  appearing  outside
       parentheses in a filename pattern.

   Globbing Flags
       There  are various flags which affect any text to their right up to the
       end of the enclosing group or to the end of the pattern;  they  require
       the  EXTENDED_GLOB  option. All take the form (#X) where X may have one
       of the following forms:

       i      Case insensitive:  upper or lower case characters in the pattern
              match upper or lower case characters.

       l      Lower  case  characters in the pattern match upper or lower case
              characters; upper case characters  in  the  pattern  still  only
              match upper case characters.

       I      Case  sensitive:  locally negates the effect of i or l from that
              point on.

       b      Activate backreferences for parenthesised groups in the pattern;
              this  does not work in filename generation.  When a pattern with
              a set of active parentheses is matched, the strings  matched  by
              the  groups  are  stored in the array $match, the indices of the
              beginning of the matched parentheses in the array  $mbegin,  and
              the  indices  of the end in the array $mend, with the first ele-
              ment of each array  corresponding  to  the  first  parenthesised
              group, and so on.  These arrays are not otherwise special to the
              shell.  The indices use the same convention  as  does  parameter
              substitution,  so that elements of $mend and $mbegin may be used
              in subscripts; the KSH_ARRAYS  option  is  respected.   Sets  of
              globbing flags are not considered parenthesised groups; only the
              first nine active parentheses can be referenced.

              For example,

                     foo="a string with a message"
                     if [[ $foo = (a|an)' '(#b)(*)' '* ]]; then
                       print ${foo[$mbegin[1],$mend[1]]}
                     fi

              prints `string with a'.  Note  that  the  first  parenthesis  is
              before the (#b) and does not create a backreference.

              Backreferences  work  with  all  forms of pattern matching other
              than filename generation, but note that when performing  matches
              on  an  entire array, such as ${array#pattern}, or a global sub-
              stitution, such as ${param//pat/repl}, only  the  data  for  the
              last  match  remains  available.  In the case of global replace-
              ments this may still be useful.  See the example for the m  flag
              below.

              The  numbering  of  backreferences strictly follows the order of
              the opening parentheses  from  left  to  right  in  the  pattern
              string,  although  sets of parentheses may be nested.  There are
              special rules for parentheses followed by `#' or `##'.  Only the
              last match of the parenthesis is remembered: for example, in `[[
              abab =  (#b)([ab])#  ]]',  only  the  final  `b'  is  stored  in
              match[1].   Thus extra parentheses may be necessary to match the
              complete segment: for example, use  `X((ab|cd)#)Y'  to  match  a
              whole  string  of either `ab' or `cd' between `X' and `Y', using
              the value of $match[1] rather than $match[2].

              If the match fails none of the parameters is altered, so in some
              cases  it  may  be  necessary to initialise them beforehand.  If
              some of the backreferences fail to match  --  which  happens  if
              they are in an alternate branch which fails to match, or if they
              are followed by # and matched zero times  --  then  the  matched
              string is set to the empty string, and the start and end indices
              are set to -1.

              Pattern matching with backreferences  is  slightly  slower  than
              without.

       B      Deactivate  backreferences,  negating  the  effect of the b flag
              from that point on.

       cN,M   The flag (#cN,M) can be used anywhere that the # or ## operators
              can  be  used  except in the expressions `(*/)#' and `(*/)##' in
              filename generation, where `/' has special meaning; it cannot be
              combined  with  other  globbing  flags  and  a bad pattern error
              occurs if it is misplaced.  It is equivalent to the  form  {N,M}
              in  regular  expressions.   The  previous  character or group is
              required to match between N and M times,  inclusive.   The  form
              (#cN) requires exactly N matches; (#c,M) is equivalent to speci-
              fying N as 0; (#cN,) specifies that there is no maximum limit on
              the number of matches.

       m      Set  references to the match data for the entire string matched;
              this is similar to backreferencing and does not work in filename
              generation.   The  flag must be in effect at the end of the pat-
              tern, i.e. not local to a group. The parameters $MATCH,  $MBEGIN
              and  $MEND  will be set to the string matched and to the indices
              of the beginning and end of the string, respectively.   This  is
              most  useful in parameter substitutions, as otherwise the string
              matched is obvious.

              For example,

                     arr=(veldt jynx grimps waqf zho buck)
                     print ${arr//(#m)[aeiou]/${(U)MATCH}}

              forces all the matches (i.e. all vowels) into uppercase,  print-
              ing `vEldt jynx grImps wAqf zhO bUck'.

              Unlike backreferences, there is no speed penalty for using match
              references, other than the extra substitutions required for  the
              replacement strings in cases such as the example shown.

       M      Deactivate the m flag, hence no references to match data will be
              created.

       anum   Approximate matching: num  errors  are  allowed  in  the  string
              matched by the pattern.  The rules for this are described in the
              next subsection.

       s, e   Unlike the other flags, these have only a local effect, and each
              must  appear  on  its own:  `(#s)' and `(#e)' are the only valid
              forms.  The `(#s)' flag succeeds only at the start of  the  test
              string, and the `(#e)' flag succeeds only at the end of the test
              string; they correspond to  `^'  and  `$'  in  standard  regular
              expressions.  They are useful for matching path segments in pat-
              terns other than those in filename generation (where  path  seg-
              ments  are  in  any  case  treated  separately).   For  example,
              `*((#s)|/)test((#e)|/)*' matches a path segment `test' in any of
              the   following   strings:   test,  test/at/start,  at/end/test,
              in/test/middle.

              Another  use  is  in   parameter   substitution;   for   example
              `${array/(#s)A*Z(#e)}'  will  remove  only  elements of an array
              which match the complete pattern `A*Z'.  There are other ways of
              performing many operations of this type, however the combination
              of the substitution operations `/' and `//' with the `(#s)'  and
              `(#e)' flags provides a single simple and memorable method.

              Note that assertions of the form `(^(#s))' also work, i.e. match
              anywhere except at the start of the string, although this  actu-
              ally  means  `anything except a zero-length portion at the start
              of  the  string';  you  need  to  use  `(""~(#s))'  to  match  a
              zero-length portion of the string not at the start.

       q      A  `q' and everything up to the closing parenthesis of the glob-
              bing flags are ignored by the pattern matching  code.   This  is
              intended  to support the use of glob qualifiers, see below.  The
              result is that the pattern `(#b)(*).c(#q.)' can be used both for
              globbing and for matching against a string.  In the former case,
              the `(#q.)' will be treated as a glob qualifier and  the  `(#b)'
              will  not be useful, while in the latter case the `(#b)' is use-
              ful for backreferences and the `(#q.)' will  be  ignored.   Note
              that colon modifiers in the glob qualifiers are also not applied
              in ordinary pattern matching.

       u      Respect the current locale in determining the presence of multi-
              byte  characters  in  a pattern, provided the shell was compiled
              with MULTIBYTE_SUPPORT.  This overrides  the  MULTIBYTE  option;
              the  default  behaviour  is  taken  from the option.  Compare U.
              (Mnemonic: typically multibyte characters are  from  Unicode  in
              the UTF-8 encoding, although any extension of ASCII supported by
              the system library may be used.)

       U      All characters are considered to be a  single  byte  long.   The
              opposite of u.  This overrides the MULTIBYTE option.

       For  example,  the  test  string  fooxx  can  be matched by the pattern
       (#i)FOOXX, but not by (#l)FOOXX,  (#i)FOO(#I)XX  or  ((#i)FOOX)X.   The
       string  (#ia2)readme specifies case-insensitive matching of readme with
       up to two errors.

       When using the ksh syntax for grouping both KSH_GLOB and  EXTENDED_GLOB
       must  be  set  and  the left parenthesis should be preceded by @.  Note
       also that the flags do not affect letters inside [...] groups, in other
       words  (#i)[a-z]  still  matches only lowercase letters.  Finally, note
       that when examining whole paths case-insensitively every directory must
       be  searched  for  all files which match, so that a pattern of the form
       (#i)/foo/bar/... is potentially slow.


   Approximate Matching
       When matching approximately, the shell keeps  a  count  of  the  errors
       found,  which  cannot exceed the number specified in the (#anum) flags.
       Four types of error are recognised:

       1.     Different characters, as in fooxbar and fooybar.

       2.     Transposition of characters, as in banana and abnana.

       3.     A character missing in the target string, as  with  the  pattern
              road and target string rod.

       4.     An extra character appearing in the target string, as with stove
              and strove.

       Thus, the pattern (#a3)abcd matches dcba, with the errors occurring  by
       using  the first rule twice and the second once, grouping the string as
       [d][cb][a] and [a][bc][d].

       Non-literal parts of the pattern must match exactly, including  charac-
       ters  in  character  ranges:  hence (#a1)???  matches strings of length
       four, by applying rule 4 to an empty  part  of  the  pattern,  but  not
       strings  of  length  two, since all the ? must match.  Other characters
       which must match exactly are initial  dots  in  filenames  (unless  the
       GLOB_DOTS option is set), and all slashes in filenames, so that a/bc is
       two errors from ab/c (the slash cannot be transposed with another char-
       acter).   Similarly,  errors  are counted separately for non-contiguous
       strings in the pattern, so that (ab|cd)ef is two errors from aebf.

       When using exclusion  via  the  ~  operator,  approximate  matching  is
       treated entirely separately for the excluded part and must be activated
       separately.  Thus, (#a1)README~READ_ME matches READ.ME but not READ_ME,
       as  the  trailing  READ_ME  is matched without approximation.  However,
       (#a1)README~(#a1)READ_ME does not match any pattern of the form READ?ME
       as all such forms are now excluded.

       Apart  from exclusions, there is only one overall error count; however,
       the maximum errors allowed may be altered  locally,  and  this  can  be
       delimited  by  grouping.  For example, (#a1)cat((#a0)dog)fox allows one
       error in total, which may not occur in the dog section, and the pattern
       (#a1)cat(#a0)dog(#a1)fox  is  equivalent.  Note that the point at which
       an error is first found is the crucial one for establishing whether  to
       use   approximation;  for  example,  (#a1)abc(#a0)xyz  will  not  match
       abcdxyz, because the error occurs at the `x',  where  approximation  is
       turned off.

       Entire   path   segments   may   be   matched  approximately,  so  that
       `(#a1)/foo/d/is/available/at/the/bar' allows one error in any path seg-
       ment.   This  is  much  less efficient than without the (#a1), however,
       since every directory in the  path  must  be  scanned  for  a  possible
       approximate  match.   It is best to place the (#a1) after any path seg-
       ments which are known to be correct.


   Recursive Globbing
       A pathname component of the form `(foo/)#' matches a path consisting of
       zero or more directories matching the pattern foo.

       As  a  shorthand, `**/' is equivalent to `(*/)#'; note that this there-
       fore matches files in the current directory as well as  subdirectories.
       Thus:

              ls (*/)#bar

       or

              ls **/bar

       does  a  recursive  directory search for files named `bar' (potentially
       including the file `bar' in the current directory).  This form does not
       follow  symbolic links; the alternative form `***/' does, but is other-
       wise identical.  Neither of these can be combined with other  forms  of
       globbing  within the same path segment; in that case, the `*' operators
       revert to their usual effect.

   Glob Qualifiers
       Patterns used for filename generation may end in a list  of  qualifiers
       enclosed  in  parentheses.  The qualifiers specify which filenames that
       otherwise match the given pattern will  be  inserted  in  the  argument
       list.

       If the option BARE_GLOB_QUAL is set, then a trailing set of parentheses
       containing no `|' or `(' characters (or `~' if it is special) is  taken
       as  a set of glob qualifiers.  A glob subexpression that would normally
       be taken as glob qualifiers, for example `(^x)', can be  forced  to  be
       treated  as  part  of  the glob pattern by doubling the parentheses, in
       this case producing `((^x))'.

       If the option EXTENDED_GLOB is set, a different syntax for glob  quali-
       fiers  is  available,  namely  `(#qx)'  where x is any of the same glob
       qualifiers used in the other format.  The qualifiers must still  appear
       at  the  end  of  the pattern.  However, with this syntax multiple glob
       qualifiers may be chained together.  They are treated as a logical  AND
       of  the  individual sets of flags.  Also, as the syntax is unambiguous,
       the expression will be treated as glob  qualifiers  just  as  long  any
       parentheses contained within it are balanced; appearance of `|', `(' or
       `~' does not negate the effect.  Note that qualifiers  will  be  recog-
       nised  in  this form even if a bare glob qualifier exists at the end of
       the pattern, for example `*(#q*)(.)' will recognise executable  regular
       files if both options are set; however, mixed syntax should probably be
       avoided for the sake of clarity.

       A qualifier may be any one of the following:

       /      directories

       F      `full' (i.e. non-empty) directories.   Note  that  the  opposite
              sense (^F) expands to empty directories and all non-directories.
              Use (/^F) for empty directories.

       .      plain files

       @      symbolic links

       =      sockets

       p      named pipes (FIFOs)

       *      executable plain files (0100)

       %      device files (character or block special)

       %b     block special files

       %c     character special files

       r      owner-readable files (0400)

       w      owner-writable files (0200)

       x      owner-executable files (0100)

       A      group-readable files (0040)

       I      group-writable files (0020)

       E      group-executable files (0010)

       R      world-readable files (0004)

       W      world-writable files (0002)

       X      world-executable files (0001)

       s      setuid files (04000)

       S      setgid files (02000)

       t      files with the sticky bit (01000)

       fspec  files with access rights matching spec. This spec may be a octal
              number optionally preceded by a `=', a `+', or a `-'. If none of
              these characters is given, the behavior is the same as for  `='.
              The octal number describes the mode bits to be expected, if com-
              bined with a `=', the value  given  must  match  the  file-modes
              exactly,  with a `+', at least the bits in the given number must
              be set in the file-modes, and with a `-', the bits in the number
              must  not be set. Giving a `?' instead of a octal digit anywhere
              in the  number  ensures  that  the  corresponding  bits  in  the
              file-modes  are  not checked, this is only useful in combination
              with `='.

              If the qualifier `f' is followed by any other character anything
              up  to the next matching character (`[', `{', and `<' match `]',
              `}', and `>' respectively, any other character  matches  itself)
              is  taken  as a list of comma-separated sub-specs. Each sub-spec
              may be either an octal number as described above or  a  list  of
              any of the characters `u', `g', `o', and `a', followed by a `=',
              a `+', or a `-', followed by a list of  any  of  the  characters
              `r',  `w',  `x', `s', and `t', or an octal digit. The first list
              of characters specify which access rights are to be checked.  If
              a  `u'  is given, those for the owner of the file are used, if a
              `g' is given, those of the group are checked,  a  `o'  means  to
              test  those  of  other users, and the `a' says to test all three
              groups. The `=', `+', and `-' again says how the modes are to be
              checked  and  have  the  same meaning as described for the first
              form above. The second list of  characters  finally  says  which
              access  rights  are to be expected: `r' for read access, `w' for
              write access, `x' for the right  to  execute  the  file  (or  to
              search a directory), `s' for the setuid and setgid bits, and `t'
              for the sticky bit.

              Thus, `*(f70?)' gives the files for which the  owner  has  read,
              write, and execute permission, and for which other group members
              have no rights, independent of the permissions for other  users.
              The  pattern `*(f-100)' gives all files for which the owner does
              not have execute permission,  and  `*(f:gu+w,o-rx:)'  gives  the
              files  for  which  the  owner and the other members of the group
              have at least write permission, and for which other users  don't
              have read or execute permission.

       estring
       +cmd   The string will be executed as shell code.  The filename will be
              included in the list if and only if the code returns a zero sta-
              tus (usually the status of the last command).

              In  the  first  form,  the first character after the `e' will be
              used as a separator and anything up to the next matching separa-
              tor  will  be taken  as the string; `[', `{', and `<' match `]',
              `}', and `>', respectively, while any  other  character  matches
              itself.  Note  that  expansions  must be quoted in the string to
              prevent them  from  being  expanded  before  globbing  is  done.
              string  is  then executed as shell code.  The string globqual is
              appended to the array zsh_eval_context the  duration  of  execu-
              tion.

              During  the  execution  of  string  the filename currently being
              tested is available in the parameter REPLY; the parameter may be
              altered  to a string to be inserted into the list instead of the
              original filename.  In addition, the parameter reply may be  set
              to an array or a string, which overrides the value of REPLY.  If
              set to an array, the latter is inserted into  the  command  line
              word by word.

              For   example,  suppose  a  directory  contains  a  single  file
              `lonely'.  Then the  expression  `*(e:'reply=(${REPLY}{1,2})':)'
              will cause the words `lonely1' and `lonely2' to be inserted into
              the command line.  Note the quoting of string.

              The form +cmd has the same  effect,  but  no  delimiters  appear
              around  cmd.   Instead,  cmd is taken as the longest sequence of
              characters following the + that are alphanumeric or  underscore.
              Typically cmd will be the name of a shell function that contains
              the appropriate test.  For example,

                     nt() { [[ $REPLY -nt $NTREF ]] }
                     NTREF=reffile
                     ls -l *(+nt)

              lists all files in the directory that have  been  modified  more
              recently than reffile.

       ddev   files on the device dev

       l[-|+]ct
              files having a link count less than ct (-), greater than ct (+),
              or equal to ct

       U      files owned by the effective user ID

       G      files owned by the effective group ID

       uid    files owned by user ID id if that is a  number.   Otherwise,  id
              specifies a user name: the character after the `u' will be taken
              as a separator and the string between it and the  next  matching
              separator will be taken as a user name.  The starting separators
              `[', `{', and `<' match the final separators `]', `}', and  `>',
              respectively;  any other character matches itself.  The selected
              files are those owned by this user.  For  example,  `u:foo:'  or
              `u[foo]' selects files owned by user `foo'.

       gid    like uid but with group IDs or names

       a[Mwhms][-|+]n
              files  accessed  exactly  n days ago.  Files accessed within the
              last n days are selected using a  negative  value  for  n  (-n).
              Files accessed more than n days ago are selected by a positive n
              value (+n).  Optional unit specifiers `M', `w', `h', `m' or  `s'
              (e.g.  `ah5') cause the check to be performed with months (of 30
              days), weeks, hours, minutes or seconds instead of days, respec-
              tively.  An explicit `d' for days is also allowed.

              Any  fractional  part  of the difference between the access time
              and the current part in the appropriate units is ignored in  the
              comparison.   For  instance,  `echo  *(ah-5)'  would  echo files
              accessed within the last five hours, while `echo *(ah+5)'  would
              echo  files  accessed  at least six hours ago, as times strictly
              between five and six hours are treated as five hours.

       m[Mwhms][-|+]n
              like the file access qualifier, except that  it  uses  the  file
              modification time.

       c[Mwhms][-|+]n
              like  the  file  access  qualifier, except that it uses the file
              inode change time.

       L[+|-]n
              files less than n bytes (-), more than n bytes (+), or exactly n
              bytes in length.

              If  this flag is directly followed by a `k' (`K'), `m' (`M'), or
              `p' (`P') (e.g. `Lk-50') the check is performed with  kilobytes,
              megabytes,  or  blocks  (of  512 bytes) instead.  In this case a
              file is regarded as "exactly" the size if the file size  rounded
              up  to  the next unit is equal to the test size.  Hence `*(Lm1)'
              matches files from 1 byte up to 1 Megabyte inclusive.  Note also
              that  the  set  of files "less than" the test size only includes
              files that would not match the equality  test;  hence  `*(Lm-1)'
              only matches files of zero size.

       ^      negates all qualifiers following it

       -      toggles  between  making  the  qualifiers work on symbolic links
              (the default) and the files they point to

       M      sets the MARK_DIRS option for the current pattern

       T      appends a trailing qualifier mark to the filenames, analogous to
              the LIST_TYPES option, for the current pattern (overrides M)

       N      sets the NULL_GLOB option for the current pattern

       D      sets the GLOB_DOTS option for the current pattern

       n      sets the NUMERIC_GLOB_SORT option for the current pattern

       oc     specifies how the names of the files should be sorted. If c is n
              they are sorted by name (the default);  if  it  is  L  they  are
              sorted  depending  on  the size (length) of the files; if l they
              are sorted by the number of links; if a, m, or c they are sorted
              by  the  time  of the last access, modification, or inode change
              respectively; if d, files in subdirectories appear before  those
              in  the current directory at each level of the search -- this is
              best combined with other criteria, for example `odon' to sort on
              names  for  files within the same directory; if N, no sorting is
              performed.  Note that a, m, and c compare the  age  against  the
              current  time,  hence the first name in the list is the youngest
              file. Also note  that  the  modifiers  ^  and  -  are  used,  so
              `*(^-oL)'  gives  a  list  of  all  files sorted by file size in
              descending order, following any symbolic links.   Unless  oN  is
              used, multiple order specifiers may occur to resolve ties.

              oe  and  o+  are  special cases; they are each followed by shell
              code, delimited as for the e glob qualifier and the + glob qual-
              ifier  respectively  (see above).  The code is executed for each
              matched file with the parameter REPLY set to  the  name  of  the
              file  on  entry  and globsort appended to zsh_eval_context.  The
              code should modify the parameter  REPLY  in  some  fashion.   On
              return,  the  value of the parameter is used instead of the file
              name as the string on which to sort.  Unlike other  sort  opera-
              tors,  oe and o+ may be repeated, but note that the maximum num-
              ber of sort operators of any kind that may appear  in  any  glob
              expression is 12.

       Oc     like  `o',  but  sorts in descending order; i.e. `*(^oc)' is the
              same as `*(Oc)' and `*(^Oc)' is the same as `*(oc)';  `Od'  puts
              files in the current directory before those in subdirectories at
              each level of the search.

       [beg[,end]]
              specifies which of the matched filenames should be  included  in
              the  returned  list.  The  syntax  is the same as for array sub-
              scripts. beg and the optional end may  be  mathematical  expres-
              sions. As in parameter subscripting they may be negative to make
              them count from the last  match  backward.  E.g.:  `*(-OL[1,3])'
              gives a list of the names of the three largest files.

       Pstring
              The  string  will  be prepended to each glob match as a separate
              word.  string is delimited in the same way as arguments to the e
              glob  qualifier described above.  The qualifier can be repeated;
              the words are prepended separately so that the resulting command
              line contains the words in the same order they were given in the
              list of glob qualifiers.

              A typical use for this is to prepend an option before all occur-
              rences  of a file name; for example, the pattern `*(P:-f:)' pro-
              duces the command line arguments `-f file1 -f file2 ...'

       More than one of these lists can be combined, separated by commas.  The
       whole  list  matches  if at least one of the sublists matches (they are
       `or'ed, the qualifiers in the sublists are `and'ed).  Some  qualifiers,
       however,  affect  all  matches generated, independent of the sublist in
       which they are given.  These are the qualifiers  `M',  `T',  `N',  `D',
       `n', `o', `O' and the subscripts given in brackets (`[...]').

       If  a  `:' appears in a qualifier list, the remainder of the expression
       in parenthesis is interpreted as a modifier  (see  the  section  `Modi-
       fiers'  in  the  section  `History  Expansion').  Each modifier must be
       introduced by a separate `:'.  Note also that the result after  modifi-
       cation  does not have to be an existing file.  The name of any existing
       file can be followed by a modifier of  the  form  `(:..)'  even  if  no
       actual  filename  generation is performed, although note that the pres-
       ence of the parentheses causes the entire expression to be subjected to
       any global pattern matching options such as NULL_GLOB. Thus:

              ls *(-/)

       lists all directories and symbolic links that point to directories, and

              ls *(%W)

       lists all world-writable device files in the current directory, and

              ls *(W,X)

       lists all files in the current directory  that  are  world-writable  or
       world-executable, and

              echo /tmp/foo*(u0^@:t)

       outputs  the basename of all root-owned files beginning with the string
       `foo' in /tmp, ignoring symlinks, and

              ls *.*~(lex|parse).[ch](^D^l1)

       lists all files having a link count of one whose names  contain  a  dot
       (but  not  those  starting  with  a  dot, since GLOB_DOTS is explicitly
       switched off) except for lex.c, lex.h, parse.c and parse.h.

              print b*.pro(#q:s/pro/shmo/)(#q.:s/builtin/shmiltin/)

       demonstrates how colon modifiers and other qualifiers  may  be  chained
       together.   The ordinary qualifier `.' is applied first, then the colon
       modifiers in order from left to right.  So if EXTENDED_GLOB is set  and
       the  base  pattern matches the regular file builtin.pro, the shell will
       print `shmiltin.shmo'.



zsh 5.0.2                      December 21, 2012                    zshexpn(1)

Mac OS X 10.9 - Generated Mon Oct 14 06:04:48 CDT 2013